5b1: guarantee the parse direction's position in the type, and name it one level deeper

src/index.ts

@@ -1,5 +1,5 @@
 export type { AdfAttributes, AdfDocument, AdfMark, AdfNode } from './adf/document.ts'
-export type { ConvertError, ConvertErrorCode, Result } from './result.ts'
+export type { ConvertError, ConvertErrorCode, ConvertErrorPath, ParseError, Result, SourcePosition } from './result.ts'
 export type { JsonValue } from './json-value.ts'
 export { adfToMarkdown } from './markdown/emit/adf-to-markdown.ts'
 export { isAdfDocument } from './adf/document.ts'